Integrating green-blue-grey infrastructure for climate-resilient cities

Cities are central to India’s economic growth. By 2030 they will generate 70% of net new jobs and more than 70% of the GDP. But cities are particularly vulnerable to climate change. On one hand, the potential financial damage from extreme climate events, heat, and drought will be staggering; the poor will bear most of the burden. On the other, cities also hold the key to altering this trajectory. Because so much of the new development (much of it greenfield) will occur in and around existing urban areas, how we imagine and plan cities will be crucial to determining the future of our planet.

Our Green Cities Initiative at CSEI, began with the premise that greening is a critical component of climate resilience. But we quickly realised that greening cities sustainably requires us to think about water bodies (blue infrastructure) and wastewater (grey infrastructure).

Green spaces are critical to low carbon development. Trees and plants sequester carbon, improve walkability and quality of life. Avenue trees, along roadsides and highways, reduce the impact of extreme heat events, which benefit the poor who walk the most. Terrace gardens and green facades provide passive cooling and reduce air conditioning load. Done right, greening can have co-benefits for pollination and biodiversity too. Urban farming can reduce food miles and improve nutritional security.

Unfortunately, most Indian cities have witnessed a steep decline in their green cover and natural resources leading to polluted and resource-scarce urban environments. Watch our video on building climate resilient cities.

Changing this will entail massive efforts towards greening public (such as roads and lakes) as well as private spaces (such as rooftops and gardens).

The question we were confronted with early on was where do we get the water from? A lot of greening projects in cities are dependent on deep borewells or scarce piped water. Piped supply is already inequitably distributed, and often space to allow greening projects is also skewed towards wealthier neighbourhoods. So expanding greening only allows the rich to capture an even greater share of the water. But irrigating green spaces with water pumped from 1000 ft deep borewells is equally unsustainable. (More on this in our blogpost: Are all green landscapes really sustainable?)

Green projects must use water resources sustainably and without worsening inequity. The good news is that most greening projects can do with lower quality water. Since 80% of water supplied to cities, returns as wastewater, treating and reusing a portion of this is a possibility. Most Indian cities treat and reuse only a fraction of their sewage. Excess treated wastewater from apartment STPs, in particular, is low in chemical contaminants. It is also high in organic content and thus ideal for greening projects.

With this understanding, our own focus within CSEI, shifted from focusing exclusively on greening as a pathway to climate resilience to looking more holistically at the green, blue, and grey infrastructure in cities.